ML20038C182

Vol II Licensing Review Group II Position Papers. Technical Discussions & Resolution of Four Licensing Review Group II Issues.Positions Taken in Papers Will Be Referenced in Plant OL Applications

ML20038C182
Person / Time
Site:	Clinton
Issue date:	12/03/1981
From:	LICENSING REVIEW GROUP II
To:
Shared Package
ML20038C179	List: ML20038C178 ML20038C182
References
NUDOCS 8112100225
Download: ML20038C182 (14)

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DECEMBER 3,1981 LRG-Il POSITION PAPERS VOLUME 11 TECHNICAL DISCUSSIONS AND RESOLUTION OF 4 LRG-Il ISSUES. THE POSITIONS TAKEN IN THESE PAPERS WILL BE REFERENCED IN LRG-il PLANT OL APPLICATIONS.

i NOTE: ADDITIONAL ISSUES WILL BE ADDRESSED IN SUBSEQUENT POSITION PAPER VOLUMES.

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TABLE OF CONTENTS LRG II POSITION PAPERS ---

VOLUME 2 ISSUE 3-RSB SRV Surveillance 1-CPB Clad Ballooning and Rupture 1-ASB Scram Discharge Volume Modifications 3-ICSB Failure of Lowest Low-Low Set Valve MJA: rf/173S1 12/3/81

LRG II Position Paper 12/3/81 3-RSB Safety-Relief Valve Surveillance Program ISSUE:

LRG II participants must commit to participate in a Safety Relief Valve

. Surveillance Program.

LRG II RESPONSE:

The LRG II position is to participate in a safety relief valve surveillance program. Such a program has been developed by the LRG I and reviewed by the BWR Owners Group for TMI and the LRG II.

LRG I, in concert with LRG II, has requested that INPO review the surveillance program and accept responsibility for centralized compilation of the required data. This request was made via the letter P. L. Powell, Chairman LRG I, to E. L. Zebroski, Vice President-INPO, dated October 27, 1981. The safety relief surveillance program, as described in the attachment to the reference letter, specifies more detailed information than required for Licensee Event Reports or for the Nuclear Plant Data Reliability System.

LRG II Position Paper 12/3/81 1-CPB Fuel Rod Cladding Ballooning and Ruoture ISSUE:

The emergency core cooling models presented in NEDE-20566 " General Electric Company Models for Loss of Coolant Analysis in Accordance with 10CFR50 Appendix K" do not provide sufficient assurance that, for the fuel cladding during the LOCA, "the degree of swelling and incidence of rupture are not underestimated". If the swelling is underestimated the cooling to the bundle may be overestimated and the peak clad temperature calculation may be non-conservative. The procedures proposed in NUREG-0630 introduce additional conservatism and should be used to perform supplemental calculations to the current ECCS analysis.

LRG II RESPONSE:

General Electric feels it is unnecessary to change the rupture strain model presented in NEDE-20566 for two reasons. First, the General Electric model is more appropriate for the BWR than the NUREG-0630 model. Second, changing the rupture strain model does not have a significant effect on peak clad temperature or clad oxidation.

LRG II Position Paper

. 12/3/81 1-CPB The report, transmitted in a letter from R. H. Buchholz (GE) to L. S. Rubenstein (NRC) dated May 15, 1981, demonstrates the adequacy of the GE model. The data used as the basis for the GE model is based on tests prototypical of BWR LOCA conditions. The GE model bounds greater than 90% of this data. The NUREG-0630 model is based primarily on data atypical of the BWR and is not appropriate for use at temperatures of interest.

The sensitivity studies, summarized in a letter from J. F. Quirk (GE) to L. S. Rubenstein (NRC) dated October 19, 1981, show that large changes assumed rupture strain will not significantly change the calculated peak temperature and clad oxidation. Excessive straining was simulated in the 10CFR50 Appendix K loss of coolant models. The models show that the increased heat transfer area of the excessively swollen rods actually caused the. peak clad temperature to decrease from the base case. Clad oxidation increased only slightly because the increased oxidation due to the larger surface area was offset by the lower temperature.

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LRG II Position Paper

. 12/3/81 1-ASB BWR Scram Discharge Volume Modifications ISSUE:

Describe the extent of conformance of the scram discharge system design to the criteria enumerated in the Generic Safety Evaluation Report (SER), BWR Discharge System dated December 1, 1980.

RESPONSE

The LRG-II position is to implement modifications to the scram discharge system that will comply with the criteria enumerated in the Generic Safety Evaluation Report - BWR Scram Discharge System.

The criteria given in the referenced SER are organized according to 1) functional, 2) safety, 3) operational and 4) design and surveillance criteria. A summary of each criteria is given below along with a discussion of how the scram discharge system complies.

Functional Criteria Functional Criterion 1 The scram discharge volume shall be sufficient capacity to receive and contain water exhausted by a full reactor scram without adversely affecting control-rod-drive scram performance.

LRG-II Compliance:

A minimum scram discharge volume of 3.34 gallons per drive is specified through the system design specifications. This minimum scram discharge volume is based on conservative assumptions as to the performance of the scram system. In the event of a coolant leak into the SDV, an automatic scram will occur before the required

SDV available is threatened.

Safety Criteria l

Safety Criterion 1 No single active failure of a component or service function shall prevent a reactor scram, under the most degraded conditions that are operationally acceptable. >

! LRG-II Compliance:

No single active failure in the scram system design will prevent a reactor scram. The scram discharge system design meets the NRC acceptance criterion for Safety Criterion 1. Partial or full loss of service functions will not adversely affect- the scram system function or will result in a full reactor scram. The system re-l

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. LRG II Position Paper 12/3/81 l 1-ASB quirements state that there shall be no reduction in the pipe size of the header piping going from the HCUs to and including the Scram Discharge Instrument Volume (SDIV). This hydraulic coupling permits operability of the scram level instrumentation prior to loss of system function. The scram level instrumentation are redundant and diverse to assure no single failure or common mode failure prevents a reactor scram.

Safety Criterion 2 No single active failure shall prevent uncontrolled loss of reactor coolant.

LRG-II Compliance:

Redundant Scram Discharge Volume (SDV) vent and drain valves are provided as part of the SDV modifications done for the LRG II plants. The redundant SDV valve configuration assures that no single active failure can result in an uncontrolled loss of reactor coolant. An additional solenoid operated pilot valve controls the redundant vent and drain valve. The vent and drain system is therefore sufficiently redundant to avoid a failure to isolate the SDV due to solenoid failure. The vent and drain valve's opening and closing sequences are controlled to minimize excessive hydro-dynamic forces.

Safety Criterion 3 The scram discharge system instrumentation shall be designed to provide redundancy, to operate reliably under all conditions, and shall not be adversely affected by hydro-dynamic forces or flow characteristics.

LRG-II Compliance:

Diverse, and redundant level sensing instrumentation on the Scram

Discharge Instrument Volume (SDIV) is provided for the automatic scram function. SDIV water level is measured by utilization of both float sensing and pressure sensing devices. Instrument taps have been relocated from the vent and drain piping to the SDIV to protect the level sensing instrumentation from the flow dynamics in the scram discharge system. Each SDIV has a redundant instrument

, loop. A one-out-of-two twice logic is employed for the automatic scram function. This instrumentation arrangement assures the automatic scram function on high SDIV water level in the event of a

, single active or passive failure. These SDV modifications will be implemented in the LRG II plants.

Safety Criterion 4 System operating conditions which are required for scram shall be l continuously monitored.

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LRG II Position Paper

. 12/3/81 1-ASB LRG-II Compliance:

See LRG-II response to Safety Criterion 3.

Safety Criterion 5 Repair, replacement, adjustment, or surveillance of any system component shall not require the scram function to be bypassed.

LRG-II Compliance:

The SDIV scram level instrumentation arrangement and trip logic allows instrument adjustment or surveillance without bypassing the scram function or directly causing a scram. Each level instrument can be individually isolated without bypassing the scram function.

3 A one-out-of-two twice trip logic is employed. LRG II plant Technical Specifications will ensure that the scram function is not bypassed during repair, replacement, adjustment or surveillance of any system component.

Operational Criteria Operational Criterion 1 Level instrumentation shall be designed to be maintained, tested, or calibrated during plant operation without causing a scram.

LRG-II Compliance:

See LRG-II response to Safety Criterion 5.

Operational Criterion 2 The system shall include sufficient supervisory instrumentation and alarms to permit surveillance of system operation.

LRG-II Compliance:

Supervisory instrumentation and alarms such as accumulator trouble, scram valve air supply low pressure, and scram discharge volume not drained alarms, are adequate and permit surveillance of the scram system's readiness.

Operational Criterion 3 The system shall be designed to minimize the exposure of operating personnel to radiation.

LRG-II Compliance:

l Minimizing the exposure of operating personnel to radiation is a j consideration in equipment design and location.

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LRG Il Position Paper

. 12/3/81 1-ASB Operational Criterion 4 Vent paths shall be provided to assure adequate drainage in preparation for scram reset.

, LRG-II Compliance:

A vent line is provided as part of the scram discharge system to assure proper drainage in preparation for scram reset. The LRG II position is to provide a dedicated vent line with a nonsubmerged discharge to the atmosphere. Furthermore, additional vent capability is provided by the vent line vacuum breakers. The vacuum breakers are required to have a differential pressure no greater than 5 inches of water.

Operational Criterion 5 Vent and drain functions shall not be adversely affected by other system interfaces. The objective of this requirement is to preclude water backup in the scram instrument volume which could cause spurious scram.

LRG-II Compliance:

The SDV vent and drain lines are required to be dedicated lines that discharge into the Radwaste System. Vacuum breakers on the SDV vent line and shut-off valves on the SDV vent and drain lines preclude water from siphoning back into the SDIV from the Radwaste System.

Design Criteria Design Criterion 1 The scram discharge headers shall be sized in accordance with GE OER-54 (Reference 20) and shall be hydraulically coupled to the instrumented volume (s) in a manner to permit operability of the scram level instrumentation prior to loss of system function. Each system shall be analyzed based on plant-specific maximum in-leakage to ensure that the system function is not lost prior to initiation of automatic scram. Maximum in-leakage is the maximum flow rate through the scram discharge line without control-rod motion, summed over all control rods. The analysis should show no need for vents or drains.

LRG-II Compliance:

As discussed in response to Functional Criterion 1, a minimum scram discharge volume of 3.34 gallons per drive is specified through the system design specifications. Furthermore, the system requirements state that there shall be no reduction in the pipe size of the MJA: rf/173J Page 4

LRG II Position Paper

. 12/3/81 1-ASB header piping going from the HCus to and including the SDIV. The SDIV shall be directly connected to the scram discharge volume at the' low point of the scram discharge header piping. These requirements satisfy NRC's acceptance criteria for Design Criterion 1.

Design Criterion 2 4

Level instrumentation shall be provided for automatic initiation while sufficient volume exists in the scram discharge volume.

LRG-II Compliance:

See Response to Functional Criterion 1 and Design Criterion 1.

Design Criterion 3 Instrumentation taps shall be provided on the vertical instrument volume and not on the connected piping.

LRG-II Compliance:

See Response to Safety Criterion 3.

Ded gn Criterion 4 The scram instrumentation shall be capable of detecting water accumulation in the instrumented volume (s) assuming a single active failure in the instrumentation system or the plugging of an instrument line.

LRG-II Compliance:

See Response to Safety Criterion 3.

Design Criterion 5 Structural and component design shall consider loads and conditions including those due to fluid dynamics, thermal expansion, internal pressure, seismic considerations and adverse environments.

LRG-II Compliance:

The SDV and associated vent and drain piping is classified as important to safety and required to meet the ASME Section III Class II and Seismic Category I requirements.

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LRG II Position Paper 12/3/81 1-ASB Design Criterion 6 The power-operated vent and drain valves shall close under loss of air and/or electric power. Valve. position indication shall be provided in the control room.

LRG-II Compliance:

The present vent and drain valve design operation meets this criterion.

Design Criterion 7 Any reductions in the system piping flow path shall be analyzed to assure system reliability and operability under all modes of operation.

LRG-II Compliance:

See Response to Design Criterion 1.

Design Criterion 8 System pip'ing geometry (i.e., pitch, line size, orientation) shall be such that the system drains continuously during normal plant operation.

LRG-II Compliance:

All SDV piping is reauired to be continuously sloped from its high point to its low point.

Design Criterion 9 Instrumentation shall be provided to aid the operator in the detection of water accumulation in the instrumented volume (s) prior i to scram initiation.

LRG-II Compliance:

The present alarm and rod block instrumentation meets this criterion.

Design Criterion 10 Vent and drain line valves shall be provided to contain the scram discharge water, with a single active failure and to minimize operational exposure.

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LRG II Position Paper 12/3/81 1-ASB LRG-II Compliance:

4 See Response to Safety Criterion 2 and Operational Criterion 3.

Surveillance Criteria Implementation of surveillance procedures to comply with the following surveillance criteria is the responsibility of the utility. The recommended Standard Technical Specifications complies with the intent of the Safety Evaluation Report's Surveillance Criteria.

Surveillance Criterion 1 Vent and drain valves shall be periodically tested.

Surveillance Criterion 2 Verifying level detection instrumentation shall be periodically tested in place.

Surveillance Criterion 3 The operability of the entire system as an integrated whole shall be demonstrated periodically and during each operating cycle, by demonstrating scram instrument response and valve function at pressure and temperature at approximately 50% control-rod density.

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LRG II Position Paper 12/3/81 3-TCSB Potential for two low-Low Setpoint Valves to Open Due to a Single Failure ISSUE:

l A single electrical failure in the low-low setpoint system hardware could cause the low and mid low-low setpoint valves to open simultaneously or to be open concurrently. This would defeat the safety design basis. The design should- be modified to correct this problem, or analyses should be presented to demonstrate that the present design is acceptable.

t LRG RESPONSE:

The probability of this event is sufficiently low and its consequences are sufficiently mild that this event need not be considered for design purposes.

The probability of occurrence of a specific failure in the low-low setpoint logic which would cause simultaneous or concurrent opening of two SRVs is 6 x 10 7/ year. This is documented in a letter from J. F. Quirk (GE) to Jim Knight (NRC) dated August 21, 1981.

LRG II Position Paper 12/3/81 3-ICSB In addition to the low probability, the consequences of such an event would not be severe. The containment load definition for multiple safety relief valve actuations is conservative by at least a factor of 2 for all frequency ranges. This was determined by comparison of Caorso test data with the results of 59 Monte Carlo simulations on the GE SRV containment load model (also documented in the reference letter). The result is also confirmed by Kuo Sheng test data and is acknowledged by draft NUREG-0802. -

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